Conversion of hydrocarbons



Filed July 1. 1953 Ill . INVENTOR. PAUL W. GARBO United States Patent ce CONVERSION OF HYDROCARBONS Paul W. Garbo, Freeport, N.Y., assignor to Hydrocarbon Research, Inc., New York, N.Y., a corporation of New Jersey Application July 1, 1953, Serial No. 365,450

7 Claims. (Cl. 208-59) This invention relates to the conversion of heavy hydrocarbons in which substantial carbonaceous matter is deposited on a particulate contact material during the con version of the hydrocarbons and this carbonaceous deposit is removed from the carrier particles by gasification. More particularly, the invention is adapted for the efiicient production of valuable hydrocarbon fractions from heavy oils, especially those having a high content of sulfur, nitrogen or metal compounds, by cracking the heavy .hydrocarbons in the presence of hydrogen.

Various processes have been proposed for converting heavy hydrocarbons to lighter hydrocarbons boiling in the gasoline range and a large proportion of these processes involve the conversion of the hydrocarbons in the presence of particulate contact material on which a carbonaceous deposit is formed by the hydrocarbons undergoing conversion and which is subjected to regeneration to remove the carbonaceous deposit. Generally, the heavier the feed hydrocarbons are, the greater is the amount of carbonaceous deposit formed on the contact material and, consequently, the greater is the problem of regenerating the contact material. Since the cost of regenerating the contact material is an important factor in the operating cost of the hydrocarbon conversion process as a whole, it is readily seen that several processes and/or hydrocarbon stocks cannot be used commercially because of the unfavorable economics of the regeneration step.

Furthermore, while it has been generally recognized that thepresence of hydrogen is beneficial to hydrocarbons undergoing high-temperature conversion in that both the yield and the quality of the hydrocarbon conversion products are improved, the high cost of known methods of producing and supplying the requisite hydrogen has thus far impeded the commercial adoption of these methods.

A principal object of the invention is to elfect economies in the regeneration of hydrocarbon contact materials and in the production of hydrogen used in hydrocarbon conversion processes.

Another important object is to remove substantial quantities of carbonaceous matter from hydrocarbon contact materials in a simple and eflicient manner while simultaneously producing hydrogen for utilization in the conversion of heavy hydrocarbons.

Additional objects and advantages of the invention will be apparentfrom the description which follows.

In accordance with the invention, hydrocarbon oil is subjected to treatment at elevated temperatures in the presence of a particulate contact material or carrier and a hydrogen-containing atmosphere, a portion of the carbonaceous matter deposited on the carrier during the conversion of the hydrocarbon feed is gasified in one re- 2,885,344 Patented May 5, 1959 generation zone by reaction with high-purity oxygen and steam at temperatures above about 1600 F. to provide the hydrogen-containing atmosphere required in the hydrocarbon conversion zone, and another portion of the carbonaceous matter on the carrier is gasified in another regeneration zone to produce a separate gaseous efliuent. The hydrocarbon conversion zone and the two regeneration zones are arranged in communication with each other so that the solid carrier particles circulate through the three zones while the gaseous efiluent from the regeneration zone which is operated to provide the hydrogencontaining atmosphere flows up through the hydrocarbon conversion zone 'and another gaseous effiuent is in dependently withdrawn from the other regeneration zone.

With the particulate carrier in a fluidized state, the hydrocarbon treatment or conversion zone and the regeneration zone in which the hydrogen-containing atmosphere is produced are preferably arranged in a single vessel with the hydrocarbon treatment zone superposed over this regeneration zone. A flow-restricting baflle structure is placed between the conversion and regeneration zones to permit the maintenance of substantially different temperatures in these zones while allowing the hydrogen-rich regeneration product gases to ascend from the regeneration zone into the conversion zone.

It is generally advisable to interpose a secondary cracking zone between the cracking zone and the hydrogen-producing regeneration zone. Preferably, the secondary cracking zone is of the type disclosed in the application of Finneran et al., Serial No. 299,114, filed July 16, 1952, wherein fiuidization of the particulate carrier is restrained in the sense that the vertical movements of the fluidized particles are restricted to the extent that a temperature gradient is established along the vertical dimension of the secondary cracking zone, ranging from the temperature of the upper cracking zone which is contiguous with the upper end of the secondary cracking zone to the higher temperature of the regeneration zone which is continguous With the lower end of the secondary zone. Such restrained fluidization is obtained by filling the secondary cracking zone with coarse packing bodies like Raschig rings and Berl saddles.

Accordingly, in a preferred embodiment of the invention, fluidized carrier particles circulate through a system which includes the primary cracking zone into which the hydrocarbon oil, preferably preheated, is fed. Conversion of the hydrocarbon oil deposits heavy hydrocarbons and carbon on the carrier particles and these particles are passed with restrained liuidization downwardly through the secondary cracking zone in countercurrent contact with a stream of regeneration product gases containing hydrogen and formed by reacting carbon with high-purity oxygen and steam at a temperature above about 1600 F. in the subjacent regeneration zone. From the secondary cracking zone, the particulate carrier passes into the subjacent regeneration zone wherein enough of the carbonaceous matter on the carrier is reacted with steam and oxygen to yield the hydrogen-containing product gases that are required in both the primary and the secondary cracking zones. Besides hydrogen, these regeneration product gases contain carbon monoxide, carbon dioxide and excess steam, and, after passing upwardly through the secondary and primary cracking zones, these gases are withdrawn together with the hydrocarbon conversion products from the top of the primary cracking zone as a single gaseous eflluent. In converting heavy hydrocarbon oils, more carbonaceous matter is deposited on the care rier than can profitably be gasified to provide the desired hydrogen in the cracking zones. If all of the hydrogencontaining regeneration product gases derived from 'all the carbonaceous matter were passed into the cracking zones, undue dilution of hydrocarbon conversion products in the total gaseous effiuent of the primary cracking zone would result, thus unnecessarily increasing the size of the recovery plant required to separate the various products in the total'gas-eous effluent. However, since in accordance with this invention only a portion of the carbon is gasified to provide the hydrogen-containing atmosphere for the hydrocarbon conversion, the carrier is also passed to another regeneration zone wherein the excess carbonaceous matter is removed by a gasifying reaction. The gases produced in the last-mentioned regeneration zone are withdrawn as a by-product stream which is independent of the production and withdrawal of the total gaseous effluent of the hydrocarbon conversion.

From the total effluent, a good yield of high octane gasoline is recovered, even when the feed stock is a heavy crude or residual oil containing large quantities of sulfur, nitrogen and metal compounds. This yield of high octane gasoline is obtained with minimum formation of hydrocarbons boiling above the gasoline range (end point of 400 F.), and these higher boiling hydrocarbons may be recycled to the conversion process to form additional gasoline or utilized as feed to a conventional catalytic cracker or sold as fuel.

In most cases, the gasoline produced by the process of this invention has a sulfur content within commercially desirable limits and is in other respects an acceptable product. In those cases where, because of the excessively poor quality of the oil treated, the gasoline produced, although of much reduced sulfur content, still contains more sulfur than is desirable or has less than the desired stability characteristics, the sulfur content and the stability characteristics can be brought to acceptable values by known refining processes, e.g., catalytic treatment of the gasoline with hydrogen at elevated temperatures.

The particulate carrier which is employed in the process of the invention is any solid heat-resistant material, such as sand, quartz, alumina, magnesia, zircon, beryl, bauxite or other like material, which will withstand the desired regeneration conditions including a temperature above 1600 F. without physically disintegrating or fusing.

The entire reaction system, i.e., all of the cracking and regeneration zones, is generally maintained at a total pressure in the range of about 150 to 800 p.s.i.g. (pounds per square inch gage), preferably 250 to 650 p.s.i.g., while a hydrogen partial pressure at least of 35 p.s.i. (pounds per square inch), preferably 75 to 150 p.s.i., is maintained in the primary and secondary cracking zones by the passage therethrough of the hydrogen-rich regeneration product gases from the gasification of a portion of the carbon formed in the hydrocarbon conversion. A hydrogen partial pressure in excess of 150 p.s.i. is not necessary since maximum benefits from the presence of hydrogen are obtained in the indicated range and there is little or no economic justification for employing a hydrogen partial pressure above 150 p.s.i. The use of total pressures in the indicated range also provides a high oxygen partial pressure in each regeneration zone thereby increasing the rate of regeneration and allows efficient recovery of the normally liquid hydrocarbon products from the total gaseous effluent.

The temperature of the primary cracking zone is maintained in the range of 850 to 1100 F., preferably 900 to 1050 F., by control of the temperature and quantity of returning regenerated carrier and by control of the temperature to which the hydrocarbon oil feed is preheated. The feed rate of hydrocarbon oil is desirably maintained at 0.2 to 3.0, preferably 0.5 to 1.5, volumes of liquid oil per hour per volume of the primary cracking zone. The

oil partial pressure, determined essentially by the rate of hydrocarbon oil feed and the volume of hydrogen-rich regeneration product gases, may vary from about 5 to 100 p.s.i., preferably from 10 to 50 p.s.i. It is a feature of the invention that the preferred range of conversion temperature is higher and the preferred range of oil partial pressure lower than are generally employed in thermal cracking processes, and as a consequence the gasoline which is produced is considerably higher in octane number than that produced in such processes, approximating CFRR octane number without use of tetraethyl lead or other anti-knock additives.

To produce the desired hydrogen-containing atmosphere, part of the non-volatile carbonaceous deposit on the particulate carrier is reacted with a regenerating gas consisting essentially of steam and oxygen, at a temperature in the range of 1600 to 2500 F., preferably 1700 to-2000" F. The regenerating gas contains a preponderance of steam and a minor proportion of high-purity oxygen, the latter more specifically containing at least about 90% by volume of oxygen, preferably at least by volume of oxygen, and obtained, for example, by air liquefaction and rectification. Steam-to-oxygen volume ratios in the range of 1.5:1 to 5:1 are generally satisfactory for generating the required quantity of hydrogen. It is preferable, as a practical matter, to employ a steamto-oxygen volume ratio of the order of 2:1 to 3:1 and thereby avoid a very high regeneration temperature. This regeneration of the carrier results in the production of a gaseous mixture comprising essentially hydrogen, carbon monoxide, carbon dioxide and excess steam, which gaseous mixture passes through the secondary cracking zone, if present, and the primary cracking zone, providing therein the desired hydrogen and acting as the principal medium for carrier fluidization.

Excess carbonaceous matter is removed from the car rier by gasification in another regeneration zone. Any oxygen-containing gas may be used. Preferably, the excess carbon is gasified with air to produce gases containing carbon monoxide, and these gases may be advantageously burned with added air to generate heat for preheating streams supplied to the process, for making steam or performing external work.

It appears that carbon which is subjected to gasification in the presence of steam at temperatures above 1600" F. undergoes activation. Accordingly, it is often desirable to leave of the order of not more than 2% by weight of the activated carbon on the carrier particles and to return such particles directly to the primary cracking zone.

To describe and explain the invention more fully, reference is made to the accompanying drawing which illustrates schematically a vertical section of two reactors adapted for carrying out the above described process.

The apparatus comprises reactor 10 having upper primary cracking zone 11, secondary cracking zone 12 filled with packing bodies, e.g., 2-inch Raschig rings, supported by grid 12a, and subjacent regeneration zone 13. Centrally disposed in reactor 10 is up-transport tube 14 which opens at its bottom near the lower end of regeneration zone 13 and at its top in primary cracking zone 11; desirably, its diameter may gradually increase from bottom to top. Lift gases are introduced into the bottom of up-transport tube 14 through tubular valve stem 15 and perforated valve body 16. Preheated steam and highpurity oxygen are introduced through inlet 17 into regeweration zone 13. Hydrocarbon oil is introduced through distributor 18 into primary cracking zone 11. Fluidized carrier particles fill reactor 10 to a height indicated by the pseudo-liquid level 11a. The reaction gases emerging at level 11a pass through cyclone separator 19 before leaving reactor 10 at outlet 19a. Carrier particles circulate in reactor 10 by flowing down from zone 11 through zone 12 into zone 13 and thence rising through tube 14 into zone 11. Carrier particles are also passed from regeneration zone 13, to auxiliary reactor 20 through transport line 21 and returned from reactor 20 to'regeneration zone- 13 through transport line 22. Slide valves 21a and 22a and aeration taps 21b and 22b are provided in lines 21 and 22, respectively, to control the rate of carrier circulation between reactors and 20. Inside reactor 20, the carrier is maintained in a dense phase fluidized bed having a pseudo-liquid level 23 above the inlet to transport line 22. Air or other oxygen-containing gas is introduced through inlet 24 at the bottom of reactor 20 and reaction gases emerging at level 23 are removed through cyclone 25 and outlet 26. Heat exchange coils, not shown, may be placed in the fluidized carrier bed in reactor 20 to recover heat of reaction, e.g., to preheat the oil or steam fed to reactor 10. If desired, an air distributor 27 may be positioned above level 23 to introduce additional oxidizing gas for converting carbon monoxide in the reaction gases to carbon dioxide. The latter combustion is advantageous where the reaction gases are to be passed through a gas turbine for the preformance of useful external work. It is advisable to have a larger horizontal cross-section in the upper end of reactor 20 to handle the larger volume of gases flowing through combustion zone 28.

In an illustrative operation of this invention, a petroleum residuum having the following characteristics:

Gravity, degrees, API Sulfur, weight percent 4.5 Carbon, Ramsbottom, weight percent 12 is treated in apparatus of the type shown in the drawing. Vessel 10 has an inside diameter of 16 feet and an overall height of 110 feet. Tube 14 has an internal diameter of 2 feet. Bauxite (100% passing through 40-mesh screen) is employed as the comminuted carrier. The total pressure in reactors 10 and is maintained at about 400 p.s.i.g.; the partial pressure of hydrogen in primary cracking zone 11 is of the order of 100 p.s.i. and is even higher in secondary cracking zone 12.

The residual oil, preheated to a temperature of 700 F., is introduced through distributor 18 at the rate of 28,000 barrels per day into primary cracking zone 11, and oxygen of 95% by volume purity and steam are introduced through inlet 17 at the rate of 10 M s.c.f.d. (million standard cubic feet per day) and 21 M s.c.f.d., respectively, to react in regeneration zone 13 with the carbonaceous deposit on the bauxite passing into zone 13 from secondary cracking zone 12. The steam-to-oxygen ratio is 2:1.

Air is supplied to reactor 20 through inlet 24 at the rate of 39 M s.c.f.d. to effect further gasification of the carbon on the bauxite. The internal circulation of bauxite through the zones in reactor 10 is effected by injecting 10 1'1 s.c.f.d. of steam through valve body 16 to lift bauxite through tube 14 at the rate of 400 tons per hour. Bauxite is also circulated between zone 13 and reactor 20 at the rate of 200 tons per hour. The oxygen and air are supplied at a temperature of 300 F. and the steam at 1000 F. The temperature is 960 F. in primary cracking zone 11 and 1800 F. in regeneration zone 13 and reactor 20. There is a temperature gradient through packed secondary cracking zone 12 ranging from the temperature of primary cracking zone 11 to that of regeneration zone 13.

The gasiform elfiuent removed through outlet 19a contains the volatile products of conversion of the residual oil admixed with regeneration product gases and excess steam. The following liquid hydrocarbon products are recovered from the effluent:

Barrels Gasoline (C and higher hydrocarbons up to 400 F.) 11,500 Light gas oil (boiling 400-750 F.) 6,800

Heavy gas oil (boiling about 750 F.) 5,100

The non-condensable portion of the efiiuent, after removing water vapor, contains on a volume basis on the order of 25% hydrogen, 25% gaseous hydrocarbons, principally methane, 20% carbon monoxide and 20% carbon dioxide.

The reaction gases of reactor 20 emerge from the fluidized mass of bauxite at pseudo-liquid level 23 at the rate of 41.5 M s.c.f.d. Approximately one-eighth of the volume of these reaction gases is carbon monoxide, the remainder being essentially nitrogen and carbon dioxide. For maximum production of useful external work, air is introduced through distributor 27 at the rate of 13 M s.c.f.d. to burn the carbon monoxide in the gases to carbon dioxide. Thus, the total product gases, essentially all nitrogen and carbon dioxide, leaving reactor 20 through outlet 26 can be fed to a gas turbine at the rate of 52.5 M s.c.f.d.

In view of the various modifications of the invention which will occur to those skilled in the art upon consideration of the foregoing disclosure without departing from the spirit or scope thereof, only such limitations should be imposed as are indicated by the appended claims.

What is claimed is:

1. The process of converting a heavy hydrocarbon oil of high Ramsbottom carbon residue which comprises converting said oil at an elevated temperature in a cracking zone in the presence of a hydrogen-containing atmosphere and particulate contact material on which a carbonaceous deposit is formed by said oil undergoing conversion, gasifying a portion of said carbonaceous deposit in one regeneration zone with steam and high-purity oxygen at a temperature of at least 1600 F. thereby forming regeneration product gases containing hydrogen, flowing all of said regeneration product gases through said cracking zone to provide therein said hydrogen-containing atmosphere, gasifying another portion of said carbonaceous deposit with air in another regeneration zone, withdrawing all of the resulting gaseous product effluent from said other regeneration zone separate from said regeneration product gases, and circulating said contact material through said cracking and two regeneration zones.

2. The process of claim 1 wherein the gasification in said other regeneration zone is carried out at an elevated temperature effective for the production of carbon monoxide.

3. The process of claim 2 wherein the gasification in said other regeneration zone is carried out at an elevated pressure of at least p.s.i.g., the resulting carbon monoxide is burned at said elevated pressure with additional air, and the hot gases of combustion are expanded with the performance of external work.

4. In the process for the conversion of heavy hydrocarbons of high Ramsbottom carbon residue wherein the hydrocarbons contact at an elevated conversion temperature a circulating mass of fluidized particles that passes through the hydrocarbon conversion zone and a regeneration zone where steam and high-purity oxygen react with the carbonaceous matter deposited on said particles in said conversion zone to form hydrogen-containing regeneration product gases, and wherein said regeneration product gases pass through said conversion zone, the improvement which comprises passing particles from said circulating mass to another regeneration zone, gasifying a portion of said carbonaceous matter on said particles with air in said other regeneration zone, returning thus partially regenerated particles to said circulating mass, and withdrawing all of the resulting gaseous product efiluent from said other regeneration zone separate from said regeneration product gases.

5. The process of claim 4 in which the temperature in said conversion zone is in the range of 850 to 1100 F., the temperatures in the two said regeneration zones are in the range of 1700 to 2000 F., and the pressure in all said zones is in the range of 150 to 800 p.s.i.g.

a hydrogen partial pressure in said cracking zone of at least 35 p.s.i. and not in excess of 150 p.s.i.

References Cited in the file of this patent UNITED STATES PATENTS Hemminger Nov. 7, 1944 Reed et a1 Sept. 7, 1948 Guyer Oct. 5, 1948 Beckberger Mar. 13, 1956 

1. THE PROCESS OF CONVERTING A HEAVY HYDROCARBON OIL OF HIGH RAMSBOTTOM CARBON RESIDUE WHICH COMPRISES CONVERTING SAID OIL AT AN ELEVATED TEMPERATURE IN A CRACKING ZONE IN THE PRESENCE OF A HYDROGEN-CONTAINING ATMOSPHERE AND PARTICULATE CONTACT MATERIAL ON WHICH A CARBONACEOUS DEPOSIT IS FORMED BY SAID OIL UNDERGOING CONVERSION, GASFYING A PORTION OF SAID CARBONACEOUS DEPOSIT IN ONE REGENERATION ZONE WITH STEAM AND HIGH-PURITY OXYGEN AT A TEMPERATURE OF AT LEAST 1600*F. THEREBY FORMING REGENERATION PRODUCT GASES CONTAINING HYDROGEN, FLOWING ALL OF SAID REGENERATION PRODUCT GASES THROUGH SAID CRACKING ZONE TO PROVIDE THEREIN SAID HYDROGEN-CONTAINING ATMOSPHERE, GASIFYING ANOTHER PORTION OF SAID CARBONACEOUS DEPOSIT WITH AIR IN ANOTHER REGENERATION ZONE, WITHDRAWING ALL OF THE RESULTING GASEOUS RPODUCT EFFLUENT FROM SAID OTHER REGENERATION ZONE SEPARATE FROM SAID REGENERATION PRODUCT GASES, AND CIRCULATING SAID CONTACT MATERIAL THROUGH SAID CRACKING AND TWO REGENERATION ZONES. 